Motion-transmitting remote control assemblies must be secure, yet adjustable for adjusting the relative length of the core element and conduit in those assemblies. Adjustment is necessary at installation to insure proper operation of a remotely controlled device through its required mechanical range of control. Periodic maintenance adjustments are also necessary to compensate for slippage and non-elastic deformation of a conduit or core element. It is important, therefore, that the adjustment means be easily adjusted and readjusted. It is also important that the adjustment means be secure; i.e., difficult to inadvertently disengage or engage. Inadvertent disengagement can cause loss of control. In certain applications, inadvertent engagement can cause damage or injury through unplanned activation and improper adjustment/regulation of a controlled device. Inadvertent engagement can also cause costly delays in assembly line processes that depend, for speed, on adjustment devices arriving from the manufacturer in a disengaged, ready-to-install state.
Unfortunately, current adjustment means that provide ease of adjustment are also relatively easy to disengage and/or engage inadvertently. A typical device allows disengagement with a single motion. The device may provide some type of securing means to hold it in a locked position, but this type of securing means is often overrideable by application of the same force and motion that would disengage the locking means.
For example, U.S. Pat. No. 5,156,064 to Truman, issued Oct. 20, 1992 discloses a cable length adjustment device comprising an elongated member, a locking member, and a housing. The housing is typically joined to, or integral with, one length of a control cable with the elongated member joined to or integral with a second length of the same control cable. The housing has a central bore formed to accommodate the end of the elongated member opposite the end attached to the second length of control cable. The housing also holds the locking member which an operator may reposition from either side of the housing. There is a bore through the longitudinal axis of the locking member to allow an operator to position the elongated member within the locking member.
When the locking member is in its locked position it prevents the elongated member from moving relative to the locking member and housing. When the locking member is rotated to its unlocked position it allows adjustment of control cable length by allowing the elongated member to move translationally relative to the locking member and housing. A ledge positioned on the locking member cooperates with a hook-like securing means positioned on the housing means to secure the locking means in its locked position. To unlock the locking means and release the elongated member, an operator (or an inadvertent external force) only need rotate the locking means with enough force to override the securing means.
Another design has securing means to prevent inadvertent disengagement of its locking means. This type of design provides additional security against inadvertent disengagement by requiring a separate motion to overcome its securing means. The design does not, however, guard against inadvertent engagement. It does not require a separate motion to disengage its securing means prior to moving the locking means out of its unlocked position. In other words, the securing means protects against inadvertent disengagement, but not inadvertent engagement.
U.S. Pat. No. 5,161,428 to Petruccello, issued Nov. 10, 1992 and assigned to Teleflex Incorporated, discloses an adjustment means of this type. It is an adjustment means for a motion transmitting remote control assembly that includes a locking clip. The locking clip is moveable between a disengaged position and an engaged position for preventing longitudinal movement between the elongated member and the base (the "base" being the functional equivalent of a "housing"). The locking clip includes two flexible fingers for bracketing and engaging the elongated member. The flexible fingers have securing means for engaging the base. Prior to extracting the locking clip from the base and disengaging the elongated member, an operator must first squeeze the distal ends of the flexible fingers together, disengaging the securing means. However, to move the locking clip out of its unlocked position, tapered surfaces on the securing means allow an operator to override the securing means and engage the locking clip by simply pressing, with a single motion, on the top surface of the locking clip. Consequently, this system has little or no protection against inadvertent engagement.